Electronics and Communication Engineering - Networks Analysis and Synthesis

31. 

In the series circuit shown in figure, for series resonance, the value of the coupling coefficient, K will be

A. 0.25
B. 0.5
C. 0.1
D. 1

Answer: Option A

Explanation:

Mutual inductance wm = ωk L1L2

m = k. 2. 8j2 = 4k. j

Z = 20 - j10 + j2 + j6 + 2.4kj - 2j + 8kj = 0 at resonance

-2 = -8k

k = 1/4 0.25 .


32. 

The degree of the nodes 1, 2, 3, 4 is

A. 2
B. 3
C. 2 for 1, 2, 3, and 3 for 4
D. all 3

Answer: Option D

Explanation:

Degree of node is the no.of branch incident to it.


33. 

In an RC series circuit R = 100 Ω and XC = 10 Ω. In this circuit

A. the current and voltage are in phase
B. the current leads the voltage by about 6°
C. the current leads the voltage by about 84°
D. the current lags the voltage by about 6°

Answer: Option B

Explanation:

In RC circuit the current leads the voltage.


34. 

The impedance of an RC series circuit is 12 Ω at f= 50 Hz. At f= 200 Hz, the impedance will be

A. more than 12
B. less than 3
C. more than 3 Ω but less than 12 Ω
D. more than 12 Ω but less than 24 Ω

Answer: Option C

Explanation:

Z = R2 + XC2. When f is made four times, XC becomes one-fourth but R remains the same.


35. 

A current is flowing through a conductor with non-uniform area of cross-section. Then

A. current will be different at different cross-sections.
B. current will be the same at all the cross-sections.
C. current will be different but current density will be same at all the cross-sections
D. current will be the same but current density will be different at different cross-sections.

Answer: Option D

Explanation:

Current density = current/area of cross-section. Same current throughout the conductor.

Since, area of cross-section is non-uniform, current density will be different at different cross-sections.